Background: Temporal arteritis is the most common systemic vasculitis in patients aged >50 years, the most serious complications of which is visual loss. The arterial biopsy is the diagnostic gold standard; alongside the classic finding of transmural infiltrate and giant cells, other abnormalities have been described, of which it is not yet known whether they identify specific clinical subsets. PET is not yet used for diagnosis, but it can be suggestive in patients with high clinical suspect; it may be useful for assessing the extention of the disease in already diagnosed patients and for ruling out alternative diagnoses as infections and neoplasms. More recently, PET has been used to assess disease metabolic activity

Objectives: The aim of our study is to evaluate, in patients with histologically confirmed temporal arteritis, correlations between pathological subsets, metabolic activity and different clinical behavior.

Methods: We have recovered the medical records of patients with the diagnosis of temporal arteritis made in our Rheumatology service from January 2007 until now. We selected those satisfying the ACR 1990 criteria and, finally, those with a positive biopsy. We analyzed age at onset of symptoms, diagnostic delay, presence of PMR, fever, constitutional symptoms, headache, temporal artery induration, visual loss; we analyzed CRP, ESR, plasmatic Hb, PLT count, hypocomplementemia, ANA, aCL, ANCA. The referring pathologist, who didn’t know the history of patients, re-examined all the biopsies performed, focusing on: transmural, periadventitial, limited to small vessels or vasa vasorum infiltrate, presence of giant cells, macrophages, eosinophils, neutrophils, lymphocytes, plasmacells, stenosis, thrombosis, fibrinoid necrosis. The nuclear doctor retrieved the PET images by re-assigning each patient the relative PET VAS score. Descriptive analysis was performed: absolute and percentage frequencies were calculated for categorical variables and mean, standard deviation, range and percentiles for quantitative variables. The relationship between variables was tested by the chi-square test and the Mann-Whitney rank test. All analyzes were performed with the STATA software 14.2.

Results: We analyzed 46 patients (F 32, M 14), average age at onset of symptoms of 75.5 yrs and average diagnostic delay of 3.2 months. Headache was reported by 37 patients, fever and asthenia by 26 and 24 respectively, jaw claudication and PMR by 18 and 7. 11 patients had visual loss while 4 and 2 respectively reported amaurosis and diplopia. Temporal artery induration was described in 24 patients. Tests of systemic inflammation were abnormal (mean CRP 85 mg/L, ESR 72.7 mm /1h); the finding of hypocomplementemia (1/26 patients), ANA, aCL and ANCA positivity (2/31, 1/27 and 1/25) was negligible. Histological analysis showed the prevalence of transmural infiltrate (100% of patients), giant cells (87%) and lymphocytes/macrophages (85% both); small vessel vasculitis (59%) and the presence of plasma cells (53%), neutrophils (48%) and eosinophils (22%) were less represented. Periadventitial infiltrate was described in 29% of patients, with negligibility of vasculitis limited to the adventitia and of the vasa vasorum (2 and 0/46). Intimal hyperplasia and necrosis (22 and 14/46) prevailed over calcifications, stenosis and thrombosis (7-5-1/46). PET was available in 14 patients including 6 positive (43%), with a median PET VAS score of 7 (range 6-21); 8/13 patients had not taken steroids prior to PET.

Conclusion: In our retrospective study we observed, in addition to transmural infiltrate and giant cells, the presence of lymphocytes, macrophages and small vessel vasculitis. No correlation was observed between clinical findings, biological and metabolic activity, apart from the increased presence of giant cells in PET positive patients. Visual loss is slightly more common in PET negative patients. This may be due to severity of the cases which needed early steroid treatment.

Disclosure of Interests: Francesco Girelli: None declared, Silvia Asioli: None declared, Riccardo Galassi: None declared, Daniela Tirotta: None declared, Chiara Bellini: None declared, Simone Bernardi Paid instructor for: Paid instructor for Pharmaceuticals in 2013, Lucia Gardelli: None declared, Linda Petrini: None declared, Elisabetta Fabbri: None declared, Paolo Muratori: None declared